Command guidance fire control systems are used to guide a missile into a target. Command guidance fire control systems track the position and motion of the missile and of the target while controlling the flight path of the missile to cause it to intercept the target. The missile is often referred to as an interceptor or interceptor platform. The target is a “non-cooperative object,” and will be referred to herein interchangeably as a target or as a non-cooperative object. The command guidance fire control system includes one or more radar systems located at a fire control sensor station of the command guidance fire control system. The fire control sensor station may be fixed (e.g., when located on or in a structure or structures) or unfixed (e.g., when located on or in a non-moving vehicle) or the fire control sensor station may be located on a moving platform, such as a ship, a tank, an airplane, etc. The command guidance fire control system also includes a receiver located on the interceptor platform and a transmitter located at the fire control sensor station.
The radar system transmits radar signals from the fire control sensor station. The radar system includes a radar sensor that detects radar signals reflected off of the non-cooperative object and off of the interceptor platform. A processor of the fire control sensor station processes the detected radar signals and determines the position and motion of the target and of the interceptor platform. The processor then computes a guidance solution. The transmitter located at the fire-control station transmits the guidance solution to the receiver located on the interceptor platform. The guidance solution is processed by a processor on the interceptor platform that causes the flight path of the interceptor platform to be adjusted, if necessary, to maintain a flight path that will intercept the target, or non-cooperative object.
One of the problems inherent in a conventional command guidance fire control system attempting to intercept a target is that the computation of the guidance solution at the fire-control sensor station and the communication of the guidance solution to the interceptor platform introduce excessive time delays between the time of determining target position and motion and the time of guidance solution command execution on the interceptor platform. These delays are attributed to: 1) the time that is required for the fire control sensor station to detect and determine the separate position and motion of both the target and the interceptor platform: 2) the time that is required for the fire control sensor station to compute the guidance solution in a coordinate frame convenient for the interceptor platform to execute guidance solution commands; 3) the time that is required for the guidance solution to be communicated from the fire control sensor station to the interceptor platform; and 4) the time that is required for the interceptor platform to process the received communication.
For the fire control sensor station to determine accurate guidance commands in a coordinate frame convenient for or suitable for use by the interceptor platform, the fire control sensor station must have knowledge about the orientation of the interceptor platform, which requires time and resources that can degrade the efficiency of the fire-control sensor station. Also, the requirement for the fire control sensor station to track the interceptor platform can introduce errors in the position and motion of the interceptor platform due to a lack of a stable reflection from the interceptor platform. These errors, in turn, introduce two-way path signal propagation spreading losses that impose signal-to-noise requirements on the command guidance fire control system that may be difficult to meet.
To address the time delay problems associated with conventional command guidance fire control systems, methods have been used to enhance guidance solution processing at the fire control sensor station processor and to improve the communication links between the fire control sensor station and the interceptor platform. One conventional method for aligning the coordinate frame of the interceptor platform with the coordinate frame of the fire control station requires that the fire control sensor station track the motion of the interceptor platform through one or more maneuvers. These jink maneuvers include one or more changes of direction to allow the fire control sensor station's estimate of the interceptor platform velocity vector to be aligned with an onboard inertial sensor estimate of the interceptor platform velocity, but generally require either communicating the interceptor platform velocity from the interceptor platform to the fire control sensor or communicating the fire control sensor station's estimate of interceptor platform velocity to the interceptor platform and performing the alignment computation in the interceptor platform processor. In either case, the coordinate alignment adds complexity and processing requirements to the command guidance fire control system.
Other solutions for addressing these issues have introduced active and semi-active seekers onboard the interceptor platform to compute the position and motion of the non-cooperative object on the interceptor platform. While these systems do mitigate timing delays and eliminate the need for jink maneuvers, they introduce another level of complexity that can impact overall system cost. In particular, these seeker solutions require alignment and calibration of the onboard sensor hardware with the on-board inertial navigation hardware that can add to complexity and cost.
In general, the existing solutions incur significant time delays due to increases in processing overhead and information sharing requirements between the fire control sensor station and the interceptor platform and/or increase onboard interceptor platform hardware complexity and cost.
U.S. Pat. No. 8,120,526 (hereinafter “the '526 patent”), which is assigned to the applicant of the present application and which discloses inventions that were invented by the inventor of the present application, discloses a guidance system in which the interceptor platform is capable of self-determining its own position and motion and the position and motion of the target, or non-cooperative object, using coded signals. While the '526 patent includes significant improvements over the above-described conventional systems, complexity and costs due to processing overhead requirements remain.